This invention relates to an improvement in the preparation of polyhydroxybutadiene (hydroxyl-containing polymers) with number average molecular weight in the range of 400 to 25,000. More specifically, the invention concerns the introduction of an aqueous solution of alkali metal sulfite or bisulfite into the polyhydroxybutadiene solvent recovery section during the preparation of polyhydroxybutadienes to prevent fouling of the acetone recovery distillation column and the azeotroping alcohol distillation column employed to recover and recycle solvent alcohol to the polyhydroxybutadiene reactors.
Processes for the preparation of polyhydroxybutadienes (hydroxy-containing butadiene homopolymers) are known in the art, and may be prepared, for example, by the methods described in U.S. Pat. Nos. 3,333,015, 3,673,168, and 3,796,762, all incorporated herein by reference.
In the preparation of polybutadiene, a solvent recovery section or unit is employed to remove the alcohol, such as isopropyl alcohol, acetone, other organics and hydrogen peroxide (H.sub.2 O.sub.2) from unreacted butadiene after removal of essentially all of the polybutadiene product. The Acetone is removed in a sieve tray distillation column and purged to waste or used as fuel. The alcohol is distilled in an azeotroping distillation column and recycled, along with some water to the reactors for reuse in the polymerization process.
A problem has existed in the polybutadiene solvent recovery unit wherein due to solids formation below the feed trays of the distillation columns, fouling occurs which plugs the trays and downcomers. The fouling is apparently caused by the presence of hydrogen peroxide, low molecular weight polybutadienes, polymeric precursors such as butadiene and vinylcyclohexene formed by the polymerization reaction. Such fouling occurres approximately every 5 to 6 days at high plant production rates thus requiring frequent and expensive shutdowns for cleaning.
The present invention of introducing a feed of aqueous alkali metal sulfite or bisulfite into the solvent recovery section provides for control of fouling of the distillation columns representing a significant improvement in the process.
Applicants are not aware of any truly pertinent prior art that is deemed to be anticipatory or suggestive of the concept of the present invention.